1. Field
Exemplary embodiments of the present invention relate to an analog-digital converter and an image sensor including the same.
2. Description of the Related Art
Analog-digital converters are generally used in an image sensor, such as a complementary metal oxide semiconductor (CMOS) image sensor, to convert a pixel signal generated from a pixel array into a pixel data.
For increasing the analog gain of a conventional analog-digital converter, a separate pre-amplifier is typically added, or the range of a ramp signal (i.e., a reference voltage) is reduced.
However, adding a pre-amplifier increases the circuit area and power consumption of the analog-digital converter. Furthermore, reducing the range of a ramp signal may also lower the level of the ramp signal, which may render the ramp signal vulnerable to noise. Hence, reducing the ramp signal range is problematic in that the signal to noise ratio (SNR) is degraded.